drbd: serialize UUID snapshot in drbd_md_write()#793
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drbd_md_write() copies device->ldev->md.uuid[] into the on-disk metadata block without holding uuid_lock. The write-side helpers drbd_uuid_new_current() and drbd_uuid_set_bm() update md.uuid[] under uuid_lock, and some updates span multiple UUID slots as one logical state transition. An unlocked drbd_md_write() can therefore observe and persist a mixed UUID tuple assembled from two different states. This is problematic because the serialized UUID tuple is written to stable storage and later consumed by reconnect and resync decision logic, meaning an inconsistent on-disk snapshot can represent a state that never existed atomically in memory. Protect the UUID copy with uuid_lock so drbd_md_write() serializes one coherent snapshot. Fixes: b411b36 ("The DRBD driver") Signed-off-by: Ziyu Zhang <ziyuzhang201@gmail.com>
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Pull request for series with
subject: drbd: serialize UUID snapshot in drbd_md_write()
version: 1
url: https://patchwork.kernel.org/project/linux-block/list/?series=1089070